FIGS. 10 and 11 show an example of the multiplex communication device by a prior art spread spectrum communication system executing high speed data communication.
FIG. 10 indicates the construction of a transmitter, in which reference numeral 1 is a serial-parallel converter; 2-1.about.2-n are multiplies; 3-1.about.3-n are PN code generators; 4-1.about.4-n are BPSK modulators; and 5 is an adder.
In the transmitter described above, inputted high speed data S1 are converted into parallel data S.sub.2 1, S.sub.2 2, . . . , S.sub.2 n by the serial-parallel converter 1. Each of the parallel data sets S.sub.2 1, S.sub.2 2, . . . , S.sub.2 n is inputted in one input of each of the multipliers 2-1, 2-2, . . . , 2-n. On the other hand, each of PN codes S.sub.3 1, S.sub.3 2, . . . , S.sub.3 n different each other outputted by each of the PN code generators 3-1, 3-2, . . . , 3-n is inputted in the other input of each of the multipliers 2-1, 2-2, . . . , 2-n. Outputs S.sub.4 1, S.sub.4 2, . . . , S.sub.4 n of the multipliers 2-1, 2-2, . . . , 2-n are inputted in the BPSK modulators 4-1, 4-2, . . . , 4-n, respectively, to modulate an RF carrier signal S5 In this way, RF signals S.sub.6 1, S.sub.6 2, . . . , S.sub.6 n are outputted by the BPSK modulators 4-1, 4-2, . . . , 4-n, respectively, which RF signals are inputted in the adder 5. An n-multiplexed spread spectrum signal S.sub.7 is outputted by the adder 5 to be transmitted.
FIG. 11 indicates the construction of the receiver, in which 7-1.about.7-n are convolvers; 8-1.about.8-n are multipliers; 9-1 - 9-n are PN code generators; 10-1.about.10-n are detectors; and 12 is a data demodulator.
In the receiver described above, a received signal S.sub.9 is divided into a plurality of signals, each of which is inputted in one input of each of the convolvers 7-1, 7-2, . . . , 7-n.
On the other hand, the PN code S.sub.10 1, S.sub.10 2, . . . S.sub.10 n outputted by each of the PN code generator 9-1, 9-2, . . . 9-n is applied to one input of each of the multipliers 8-1, 8-2, . . . , 8-n. An RF carrier signal S.sub.13 is inputted in the other inputs of the multipliers 8-1, 8-2, . . . , 8-n. The output S.sub.11 1, S.sub.11 2, . . . , S.sub.11 n of each of the multipliers 8-1, 8-2, . . . , 8-n is applied to one input of each of the convolvers 7-1, 7-2, . . . , 7-n.
The outputs S.sub.12 1, S.sub.12 2, . . . , S.sub.12 n of the convolvers are inputted in the detectors 10-1, 10-2, . . . , 10-n, respectively. At this time, as indicated in FIG. 12, in the outputs of the convolvers correlation spikes are produced with a same timing for different data channels. The outputs S.sub.15 1, S.sub.15 2, . . . , S.sub.15 n of the detectors 10-1, 10-2, . . . , 10-n are inputted in the data demodulator 12. Demodulated data S.sub.16 are outputted by the data demodulator 12.
The prior are multiplex communication device described above has drawbacks that it is necessary to synchronize the carriers and that a plurality of convolvers (or matched filters) serving as correlators are required.